If u=(ax+by)²-(x²+y²) and a²+b²=1 then u_xx+u_yy=

If V=πr²h then rV_r+2hV_h=

If u=x²+y²+z²,x=e^t,y=e^t sin t,z=e^t cos t then du/dt=

If u³(1+a³)=8(x+ay+b)³ then u³_x+u³_y=

If f(x,y)=xy+(1/x)+(1/y) then f_xx?f_yy-f_xy² at (1,1) is

If r²=(x-a)²+(y-b)² then r_xx+r_yy=

If f(x,y)=x²Tan^-1(y/x)-y² Tan^-1(x/y),x≠0,y≠0 then f_xy=

If V is the volume of a rectangular box with edges x,y,z then V_xyz=

If f=x²yz+y²zx+z²xy then f_xyz=

If z(x,y) is the implicit function defined by x³+y³+z³=3xyz then xz_x+yz_y=